1. Field of the Invention
The present invention relates to an ink jet head and an ink jet recording device.
2. Description of the Related Art
As a typical desktop nonimpact recording device, an ink jet recording device is now receiving attention for reasons of simple manufacturing and easy realization of full-color recording. The ink jet recording device has a recording head provided with a plurality of pressure chambers. A piezoelectric element or a resistive heating element, for example, as an actuator is built in each pressure chamber. Each pressure chamber is partially defined by a nozzle plate. The nozzle plate is formed with a plurality of nozzles respectively corresponding to the pressure chambers.
Ink is supplied from a common ink chamber through a plurality of ink supply channels respectively to the pressure chambers. When the actuator is driven, a pressure wave is generated in the corresponding pressure chamber to eject ink droplets from the corresponding nozzle, thus effecting dot recording on a recording medium such as a sheet of paper. In an existing ink jet head, the ratio of the mass of ink in each nozzle and the mass of ink in each ink supply channel is preferably set in the range of about 1:1 to about 1:2. Further, the diameter of each nozzle is preferably set to about 30 .mu.m in consideration of printing speed, resolution, etc.
In the case of deciding the dimensions of each ink supply channel so as to meet the above conditions, the length of each ink supply channel is set to less than 100 .mu.m provided that the sectional shape of each ink supply channel is circular or square. If the length of each ink supply channel is not less than 100 .mu.m and the sectional shape thereof is square, the viscosity of ink in each ink supply channel is too small, causing a reduction in balance between the ink mass in each nozzle and the ink mass in the corresponding ink supply channel. Accordingly, in the case of setting the length of each ink supply channel to not less than 100 .mu.m, the sectional shape of each ink supply channel is set oblong.
FIGS. 1A and 1B illustrate a prior art ink jet head having short ink supply channels each having a length less than 100 .mu.m. Reference numeral 1 denotes a pressure chamber plate formed with a common ink chamber 2 and a plurality of pressure chambers 3. Each pressure chamber 3 is connected through an ink supply channel 4 to the common ink chamber 2. A nozzle plate 6 having a plurality of nozzles 7 is bonded to the pressure chamber plate 1. Reference numeral 8 denotes an ink droplet ejected from one of the nozzles 7. In the case that the thickness of a partition wall 5 formed between the common ink chamber 2 and each pressure chamber 3, that is, the length of each ink supply channel 4 is set to less than 100 .mu.m as mentioned above, good flying characteristics or frequency characteristics of ink can be realized by setting the sectional shape of each ink supply channel 4 substantially square. However, in the case of integrally forming the common ink chamber 2, the pressure chambers 3, and the ink supply channels 4 on the pressure chamber plate 1, the manufacture of the ink jet head becomes difficult with the thickness of the partition wall 5 set to less than 100 .mu.m.
FIGS. 2A and 2B illustrate another prior art ink jet head having long ink supply channels each having a length not less than 100 .mu.m. As shown in FIG. 2A, the length of each ink supply channel 4', that is, the thickness of a partition wall 5' is set to not less than 100 .mu.m. In this case, the sectional shape of each ink supply channel 4' is set oblong as shown in FIG. 2B in consideration of the balance between the ink mass in each nozzle 7 and the ink mass in the corresponding ink supply channel 4'.
As mentioned previously, in the case of integrally forming the common ink chamber, the pressure chambers, and the ink supply channels on the pressure chamber plate, the manufacture of the ink jet head becomes very difficult with the length of each ink supply channel, or the thickness of the partition wall between the common ink chamber and each pressure chamber set to less than 100 .mu.m. Further, in the case of setting the length of each ink supply channel to not less than 100 .mu.m, the sectional shape of each ink supply channel 4' becomes oblong as shown in FIG. 2B in consideration of the balance between the ink mass in each nozzle and the ink mass in the corresponding ink supply channel. However, when the sectional shape of each ink supply channel is oblong, a turbulent flow is likely to generate in each ink supply channel, causing a deterioration in flying characteristics or frequency characteristics of ink.